Contact structure



Allg. 194.6. R E, FR|EDR|CH 2,406,327

' CONTACT STRUCTURE l Filed Dec. 2e, 1942 Patented Aug. 27, 1946 COTA'CT STRUCTURE l Robert E. Friedrich, Pittsburgh 16, Pa., assgnor I to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 26, 1942,V Serial No. 470,159

6 Claims.

This invention relatesv to `'contact structures and, more particularly, to the art of attaching contacts of preciousmetals and refractory metals 'and their alloys to supportingrstructures of ybase metal.

It 4isrdesirable to lmake the-contacts for use on high-speed lcircuit interrupters of a light, electrically conducting metal selected 'from the group consisting of aluminum, magnesium vand their alloys, such as zinc, silicon or copper, in order to provide a m-inmum Weight. An example of an alloy `which hasbeen found satisfactory for the 'main 'contact member consists of QLD/2% laluminum and 4.1/% cc'lpper. Such metals are unsuitable ror use :as an arcing contact. Heretofore it has been common ypractice to secure an arcing tip of arc-resisting material to the main contact element in order to prevent excessive burning of the contact. Such karc-resisting Y materials usually consist of copper-tungsten r silvertungsten mixtures formed to provide a refractory contact tip 'which satisfactorily resists the damaging' veffects of current arcs. Great difficulty has been encountered in attaching arc-resisting contact tips to such contact members, since these arc-resisting materials do not braze satisfactorily to such metals. In trying to obtain goed mechanical and electrical connections oiE such arcing tips to contact structures of aluminum, magnesium and their alloys, various 'methods yof attaching the arcing tips to the contact structure have been resorted to. Such methods include riveting, swaging, or soldering, etc. It has been found, however, that repeated hammering 'of the contact tips, due to repeated operation of the interru'pter, has a tendency to loosen-swaged tips and riveted vtips and to crack the soldered ljoints, thus introducing high resistance Where the 'arcing' occurs and to thereby further impair the efficiency of the contact.

The principal object of the instant invention is the provision of an improved contact structure wherein an arc-resistant tip is secured to a contact member of aluminum, magnesium and their alloys in a manner to provide maximum mechanical strength and electrical conductivity.

Another object of the invention is the provision of an improved contact assembly.

Another object of the invention is the provision of an improved method of attaching an arcresisting contact tip to a support or contact member of aluminum, magnesium and their alloys.

Another object of the invention is the provision of an improved contact structure of low mass (c1. I20o- 166) 2 having "an arcingV tip of arceresisting material which'provides great mechanical strength, high conductivity and which requires a minimum amount olf arc-resisting material.` These and other objects and advantages ofthe invention will appear from the following detailed description ofl one embodiment thereof whenvrea'd in connection with the accompanying drawing, in which:

Figure 1 is aside view, partly in se'ction,lof-a'n arcing tip adapted to be assembly; c

Fig. 2 is a side view of` a 'flanged screw adapted to receive the arcing tip shown in Fig.-1"; h

Fig. 3 is an elevational vi'ew,rpartly in section, showing the main contact body; I

Fig. 4 is an elevational view of the arcing contact attached to the head o'f the screw; and

Fig. 5 is an elevational View, partly in section, showing the completed contact assembly.

According to the invention, a contact II (Fig. 1) of an arc-resisting material, such, for example, as pressed and sintered mixtures of coppertungsten or silver-tungsten or other known arcresisting materials, is formed substantially as illustrated, having a projection I3 inthe shape of a truncated cone integral therewith. Since it has been found exceedingly difficult to obtain a satisfactory joint between such arc-resisting materials and aluminum, magnesium and their alloys, the arcing contact II is secured by brazing to the lianged head I5 lof a screw or bolt I1 com'- posed of a metal to which it mayr readily and strongly be brazed, such, for instance, as brass. Bra'zing the arcing tip l I to the bolt I1 is accomplished by means of a high-strength brazing material, such as silver solder.

The main body I9 (Fig. 3) of the contact struc ture, which is of aluminum, magnesium and their alloys, is prepared to receive the arcing tip assembly (Fig. 4) by drilling a hole 2l axially through the center of the member. 'Ihis opening is tapped from the contact end a distance sufficient to receive the threaded bolt I 1. The tapped end of main contact member I9 is then counterbored as at 23, the counterbore having a diameter substantially equal to the diameter of the annular projection formed by the projection I3 and the flanged head I5 of the bolt I'I. The counterbore 23 provides the member I9 with a conical shoulder 25 having the same angle with reference to the axis of the member I9 as the angle of the flanged head with reference to the axis of the bolt I1.

All of the surfaces of the assembly illustrated attached to the contact y l' groove, formed by the swaging in Fig. 4 andV of the main metal comprising the shoulder V29 'of the mainY contact member is forced into the groove defined by the bottom of the contact-tip II andthe pro' jection I3 thereof by a swaging operation. The

complete assembly (Fig. 5,) 'is then passed through Y a suitable welding furnace and 'brought to Welding temperature .suiciently high to melt the brazingmaterial with which. the contactingsurfaces were coated. Thus' all of the contacting surfaces of the members Il, l1 and I9 Yare firmly brazed orwelded together.

After vthis brazing operation, the annular toolbetween the arcing contactand the shoulder 29 of the main contact member I9, is lled with solder as at 3| (Fig. 5) to providebetter conductivity and a flush smooth surface to the contact assembly.

It can be seen that a contact assembly made in accordance with procedure set forth has great mechanical strength and is capable of withstanding repeated heavy blows, and also has a maximum of electrical conductivity due to the brazing of all contacting surfaces.

contact member, whichwill come into contact with each other, are next it securely in the in lthe member' I9, the` Yinto the annular grooveprojection and securelyhold all of the parts to- 4 ing a anged head to which said contact member is attached, said projection and said head forming an annular projection, a support member of a light, electrically conducting metal selected from the group consistingl nesium and their alloys, said support member having an opening in which said screw and said contact members are threacledlyv'Y mounted, said opening forming a shoulder on k'saidsupport mem.

ber, said shoulder having Va portion extending 3'. Acntact assemblyV l intermediate member, a contact of arc-resisting' material secured to said intermediate' member by l brazing, said threaded member and said contactV y forming an annular'projection, a' support member of a light, electrically conducting metal selected from the group consisting of aluminum,

magnesium andtheir alloys; SaidV support memy berhaving' a threaded opening in which said'intermediatev member is threadedly mounted, a part of said support member embracing said projection to form a rigid mechanical connection between all of said members, the Yadjoining surfacesof said members having a coatingofbrazing mate-'j rial to integrally secure said members togethen 4.' A contact assembly comprising a contact member of arc-resisting material anda threaded support member brazed thereto, said members forming an' annular projectio and a member having a threaded opening in which said support Having described a preferred embodiment of Y fcha'nges and modifications may be `made therein without departing from the spirit of the invention. It'is, therefore, desired'that the language of vthe/appended claims be given as reasonably broad interpretation as the prior art permits. l

l. claim as my invention: 'Y 1. AV contact assembly comprising a contact member oi'arc-resisting material, a screw having a flanged head to which said` contact member is brazed, said iianged head together withV a part of said contact member forming an annular projection, asupport member having an opening in which said screw and a part of said contact members are threadedlyl mounted, a portion of said support member embracing said projection to hold vthe parts together. A

2. A contact assembly comprising a contact member of arc-resistingv material having a projection forming an annular groove, a screw havmember and said annular projection are mounted,

a portion of said support memberextendingover saidv projection and a part of said contact member.

5. A Contact member eral groove formedtherein, a headed screwbrazed to said contact member, a member having'a threaded and counterboredy recess for receiving said screw and a part of said contact, a portion of said member extending into the peripheral groove in the contact member, and the adjoining surfaces of'the contact member, the'screw vand assemblyY comprisingY a 4contact the memberbeing rintegrally. secured together by a brazing material.

6. A contact assembly comprising a contact member of a light, electrically conducting metal selected from the group consisting of aluminum, magnesium and'their alloys, said contactmember having a threaded opening in'one end thereof, a metal screw mounted in said opening, and a contact tip of arc-resisting material brazed on the head of said screw, the end of said contact member having a portion swaged over against a portion of said contact tip.

VROBFR'I E; FRIEDRICH. J

of aluminum, magy to embrace said annular f comprising a threaded Y ofrefractory material having a periph- 

